Compression socks apply gentle pressure to the lower legs, promoting better blood flow back toward the heart. This pressure is measured in millimeters of mercury (mmHg), the same unit used for blood pressure. The mmHg value indicates the pressure applied, which is typically highest at the ankle and gradually decreases further up the leg. Understanding this measurement is the first step in selecting the correct strength for effectiveness and safety.
Mild Compression for Everyday Wellness
The lowest compression levels are generally available over-the-counter for daily wear and minor symptoms. The mildest range is 8–15 mmHg, which provides light support for tired or achy legs. This strength is commonly used for comfort during long periods of sitting, such as while working at a desk or traveling.
The 15–20 mmHg range is the most common for general wellness and is widely available without a prescription. This moderate level provides noticeable relief for fatigue, slightly swollen legs, and minor ankle swelling. Healthcare providers suggest starting with 15–20 mmHg for first-time wearers or those seeking enhanced circulation during physical activity or recovery.
This strength is also frequently recommended during pregnancy to help manage minor swelling (edema) and prevent the formation of new varicose or spider veins. For individuals who spend extended periods on their feet or travel frequently, this range helps support the veins and minimize the risk of developing deep vein thrombosis (DVT). These mild and moderate strengths are generally safe for most people, provided the sock fits correctly, but they are not intended to treat serious circulatory issues.
Moderate and Firm Strengths for Clinical Needs
Compression levels of 20 mmHg and above are considered medical-grade. The 20–30 mmHg range is the first level prescribed by a healthcare provider for conditions like chronic leg pain, moderate edema, and varicose veins. This strength is also used after vein procedures, such as sclerotherapy, to prevent treated veins from reappearing.
For more severe venous issues, the 30–40 mmHg range is required. This firm compression treats severe edema, lymphedema, and chronic venous insufficiency. It may also be used to manage active DVT or to help heal venous stasis ulcers.
Higher compression levels (40–50 mmHg) are reserved for the most serious venous diseases and must be used under the direct supervision of a doctor. Using these high strengths without medical guidance carries risks, as they can worsen circulation if an underlying arterial issue is present. Consult a healthcare provider before using any compression sock 20 mmHg or higher to ensure correct diagnosis and prevent complications.
Ensuring Proper Fit: Measurements and Sizing
The compression strength alone is insufficient if the sock does not fit properly, rendering the garment ineffective or uncomfortable. To ensure maximum benefit, the leg must be measured to match the manufacturer’s sizing chart. A correct fit ensures the graduated pressure applies the intended force at specific points along the limb.
The three required measurements are the circumference of the ankle, the circumference of the calf, and the length of the leg. The ankle circumference should be taken at the narrowest point, just above the ankle bone, where the highest compression pressure is applied. The calf measurement is taken at the widest part of the calf muscle.
For knee-high socks, the leg length measurement extends from the heel to the bend of the knee. It is recommended to take these measurements first thing in the morning, immediately after waking. Swelling increases throughout the day due to gravity, and measuring later can result in a sock size that is too large, reducing the intended compression and therapeutic effect.